1. Field of the Invention
This invention relates to a disk format on optical disk, and to an optical disk device that can conduct the recording and playback of such an optical disk.
2. Background of the Invention
In recent years, for a rewritable optical disk with a large capacity, a land/groove recording system that a region between grooves is also used as an information track, as well as a groove provided as a guide trench on optical disk is suggested. The land and groove may be called convex part and concave part, respectively, or called inter-groove part and groove part, respectively. First, an optical disk used in the conventional land/groove recording system is explained.
FIG. 1 is a partial enlarged plan view showing a conventional optical disk that is described in Japanese patent No. 2,663,817. In FIG. 1, G indicates a groove region, L indicates a land region, Tp indicates a track pitch, P indicates a pre-pit, and BS indicates a focused beam spot. Also, xe2x80x9cidentification signal regionxe2x80x9d in Japanese patent No. 2,663,817 is called xe2x80x9cheader regionxe2x80x9d herein. In this disk format, a header region including address information is shared between adjacent groove G and land L, and at least a part of information signal included in header region is shifted by Tp/4 to the center line of groove G and to the center line of land L, and in at least part of optical disk, the header region and recording data region each are formed in a radial pattern.
FIG. 2 is a block diagram showing the composition of an optical disk device used for the optical disk above. In FIG. 2, 100 is the optical disk, 103 is a half mirror serving as a beam splitter, 104 is an objective lens to converge collimated light passed through the half mirror 103 onto the optical disk 100, 105 is a collimator lens to collimate light from a semiconductor laser 106, and 108 is an optical detector to receive reflected light from the optical disk 100 passing though the objective lens 104 and the half mirror 103. The optical detector is composed of two light-receiving parts that are divided in parallel to the track direction (tangential direction of circumference) of the optical disk to obtain the tracking error signal. 102 is an actuator supporting the objective lens 104. Meanwhile, part 101 enclosed by a dotted line in FIG. 2 is attached to a head base (not shown), and compose an optical head.
On the other hand, 110 is a differential amplifier to which detection signal to be output from the optical detector 108 is input. 117 is a polarity inverter to which tracking error signal from the differential amplifier 110 and control signal L4 from a system controller 118 described later are input, and which controls the polarity of tracking error signal output to a tracking controller 116 according to the control signal L4. Hereupon, regarding the polarity of tracking control, when tracking error signal is input, with its polarity unaltered, from the differential amplifier 110 to the tracking controller 116, the tracking is pulled into the recording track of groove G. 116 is the tracking controller to which output signal from the polarity inverter 117 and control signal L1 from the system controller 118 are input, and which outputs tracking control signal to a driver 122 and a traverse controller 121. 109 is an adder amplifier to which detection signal output from the optical detector 108 is input and which outputs add signal. 112 is a waveform shaper to which a RF component from the adder amplifier is input, and which outputs digital signal to a playback signal processor 113 and a address playback circuit 114. 113 is the playback signal processor which outputs playback data to the output terminal. 114 is the address playback circuit to which digital signal from the waveform shaper 112 is input, and which outputs address signal. 115 is an address calculator to which address signal from the address playback circuit 114 and control signal L4 from the system controller 118 are input, and which outputs address signal to the system controller 118.
Also, 121 is the traverse controller which outputs drive current according to control signal from the system controller 118. 107 is a traverse motor which moves the optical head 101 in the radius direction of the optical disk 100 according to drive current from the traverse controller 121. 119 is a record signal processor to which record data is input and which outputs record signal to a laser (LD) driver 120. 120 is the LD driver to which control signal from the system controller 118 and record signal from the record signal processor 119 are input, and which supplies drive current to the semiconductor laser 106. 122 is the driver to which tracking control signal from the tracking controller 116 is input and which supplies drive current to the actuator 102. Meanwhile, the system controller 118 which outputs control signal L1, L4 to the tracking controller 116, the traverse controller 121, the address calculator 115, the polarity inverter 117, the record signal processor 119 and the LD driver 120, and to which address signal from the address calculator 115 is input.
The operation of the conventional optical disk device thus composed is explained below.
Light output from the semiconductor laser 106 is collimated by the collimator lens 105, passed through the beam splitter 103, converged onto the optical disk 100 by the objective lens 104. Laser light reflected on the optical disk 100 holds the information of record track, passing through the objective lens 104, being led through the beam splitter 103 to the optical detector 108. The optical detector 108 converts a variation in light quantity distribution of light beam supplied into electrical signal, outputting it to the differential amplifier 110, the adder amplifier 109. The differential amplifier 110 current-voltage-converts (I-V conversion) currents input, taking the difference of both voltages, outputting it as push-pull signal. The polarity inverter 117 judges whether the track accessed is a land or a groove according to control signal L4 from the system controller 118, inverting the polarity, for example, only when the track is a land. The tracking controller 116 outputs tracking control signal to the driver 122 according to the level of tracking error signal input, the driver 122 supplies current to the actuator according to this signal to control the position of the objective lens 104 in the radius direction across the recording track. Thereby, the optical spot can scan precisely on the track.
On the other hand, the adder amplifier 109 current-voltage-converts (I-V conversion) two currents output from the light-receiving part 108, adding both, outputting it as add signal to the waveform shaper 112. The waveform shaper 112 shapes data signal and address signal with an analogue waveform into a pulse waveform by data-slicing by a certain threshold value, outputting it to the playback signal processor 113 and the address playback circuit 114. The playback signal processor 113 demodulates digital data signal input, conducting the processing of error correction etc. to output it as playback data. The address playback circuit 114 demodulates digital address signal input, outputting it as position information on the disk to the address calculator 115. The address calculator 115 calculates the address of a sector accessed from address signal read out from the optical disk 100 and land/groove signal from the system controller 118. The calculation method is to judge referring to an address map etc. and then output the judgement signal.
The system controller 118 judges whether the light beam currently locates at a desired address based on this address signal. The traverse controller 121 outputs drive current to the traverse motor 107 according to control signal from the system controller 118 when shifting the optical head 101, thereby the optical head 101 is shifted to a target track. Hereupon, the tracking controller 116 suspends the tracking servo according to control signal L1 from the system controller 118. Also, in the normal playback mode, the traverse motor 107 is driven according to tracking error signal input from the tracking controller 116, and the optical head 101 is moved gradually in the radius direction as the playback operation proceeds. The record signal processor 119 adds an error correction code etc. to record data input, outputting it as encoded record data to the LD driver 120. When the system controller 118 sets the recording mode by control signal, the LD driver 120 modulates drive current applied to the semiconductor laser 106 according to record signal. Thereby, the intensity of light spots projected onto the optical disk 100 varies according to the record signal, record pits are formed. On the other hand, in the playback operation, the LD driver 120 is set to the playback mode by control signal, the drive current is controlled so that the semiconductor laser 106 emits light at a constant intensity. Thereby, the detection of record pit and pre-pit on record track is enabled.
Meanwhile, Japanese patent No. 2,663,817 discloses not only a technique that the detection of record pit and pre-pit is conducted using track add signal but also a way to detect a pre-pit using push-pull signal which is track difference signal. Namely, since the header region is positioned offsetting by Tp/4 from the record track in the radius direction, the detection using push-pull signal is enabled.
However, the optical disk and optical disk device using the land region and groove region as an information track have a significant weakness for the defocusing of focused beam. Namely, due to an error in the manufacturing of head or a deterioration in head performance with age, so-called defocusing that focused beam is converged deviating from a right focus position occurs. Hereupon, in the optical disk described above, information of adjacent header regions affects as a crosstalk. Especially, when one address information is a signal of short mark and other to crosstalk is a signal of long mark, a significant distortion of waveform is observed and an error in the reading of address information occurs. In this case, since the header region needs to be played back while waiting for the rotation, the throughput may be reduced. Also, when it is played back again, the reading error is highly like to recur. Therefore, since it may be registered as a defect sector, the reliability of device and disk must be thus reduced.
Also, in the optical disk device above, since the header region including address information is shared between adjacent groove and land, when an address to start the recording/playback is designated, the system controller judges whether the designated address is the land region or groove region by referring to an address map etc. Then, judgement signal (polarity signal) is output to the tracking servo system. After the tracking, detection signal of the physical address is address converted by the judgement signal, thereby it is judged whether the tracking is carried out to the designated address. However, for example, when a large track offset occurs due to the failure of tracking, the tracking to the land or groove may not be performed as designated by polarity signal. Therefore, the judgement of address becomes unsuccessful and the operation of device goes out of control.
Also, in the header region, the influence of the pre-pit to servo error signal is to cause the focus offset and the disorder of track error signal, thereby incurring a unstable recording/playback. At the same time, when starting the recording after passing the header region, depending on the composition of optical head, there occurs a focus offset due to the chromatic aberration of objective lens, by a phenomenon called a jump of wavelength in semiconductor laser. This focus offset interferes with the focus offset occurring near the header region, thereby the focus control is made to be further unstable, causing a failure in recording.
Accordingly, it is an object of the invention to provide an optical disk with an enhanced reliability.
It is a further object of the invention to provide an optical disk device with an excellent stability of recording/playback.
According to the invention, an optical disk, comprises:
a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal; and
a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including specific information;
wherein the specific information""s in neighboring pre-pit regions are not aligned in the radius direction of the optical disk.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
means for outputting, in advance, as identifier 1 whether a recording track scanned by light beam is a land region or a groove region;
a track region detection means for detecting whether the recording track scanned by light beam is a land region or a groove region and outputting the detection result as identifier 2;
an address information extraction means for extracting address information from the pre-pit region scanned by light beam; and
means for conducting the address calculation by receiving the inputs of the identifier 1, identifier 2 and address information.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
a track region detection means for detecting whether a recording track scanned by light beam is a land region or a groove region;
means for detecting a push-pull signal as a track difference signal based on the output of the track region detection means;
a calculation means for calculating the track difference signal by setting a subtraction ratio between one signal output and other signal output of the two signal outputs used to calculate the track difference signal; and
means for detecting address information from the output of the calculation means.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
a header region detection means for outputting header region signal to indicate the position of a header region including the pre-pit region from a track add signal;
means for outputting first-order differential signal from a push-pull signal as a track difference signal;
means for outputting differential cross signal from the zero cross signal of the first-order differential signal;
a window comparator means for binarizing the amplitude of the first-order differential signal at a predetermined slice level; and
a logical operation means for outputting track region detection signal to determine whether a track scanned by light beam is a land region or a groove region, from the header region signal, differential cross signal and output signal of the window comparator means.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
means for outputting signal to detect whether a recording track scanned by light beam is a land region or a groove region;
a header region detection means for detecting a header region including the pre-pit region; and
a servo error detection means for sampling a track error signal value at an arbitrary time before the output time of the header region detection means, and holding the track error signal value an arbitrary time or conducting an operation of the track error signal value and arbitrary waveform signal then outputting the operation result as servo error signal.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
means for outputting signal to detect whether a recording track scanned by light beam is a land region or a groove region;
a header region detection means for detecting a header region including the pre-pit region; and
a servo error detection means for sampling a focus error signal value at an arbitrary time before the output time of the header region detection means, and holding the track error signal value an arbitrary time or conducting an operation of the focus error signal value and arbitrary waveform signal then outputting the operation result as servo error signal.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
means for outputting envelope signal or peak hold signal from track add signal to be input;
means for binarizing the envelope signal or peak hold signal to be input;
a burst detection means for detecting burst signal with a specific mark included in the pre-pit region then outputting burst detection signal; and
a logical operation means for outputting binarized signal nearly enclosing the pre-pit region based on the output signal of the binarizing means and the burst detection signal.
According to another aspect of the invention, an optical disk device for conducting the recording/playback of an optical disk comprising a land region and a groove region that are formed on a substrate, the land region and groove region being used as a recording track that is the medium of the recording/playback of information signal, and a pre-pit region that is formed at the boundary part of neighboring land region and groove region and is disposed every other boundary part, the pre-pit region including address information, comprises:
means for generating replica signal under a condition that a crosstalk component from the neighboring pre-pit region at a position where address information is played back is clearly detected; and
a crosstalk removing means for removing the replica signal as crosstalk component from a signal component played back.